Hello Wirik,
Thank you for reaching out to the Microsoft Community and I'll be glad to assist you today.
No, clicking the Reset Button will not delete the virus definitions or security updates that are already installed.
This option will reset the Windows Security App's settings and configuration, which resolves any app-related issues like launching or freezing during the system scan.
The line "the system component's data will be deleted" refers to the app's settings and local cache, not critical security components like virus definitions or Windows updates.
After resetting, the app will still continue to use the latest virus definitions and security updates.
I hope this information helps. If you have any questions, please let me know and I will be happy to help you further.
Best regards,
Gunasekar N